Apparatus for air impingement starting of a turbojet engine



June 27, 1961 P. R. PAIEMENT 2,989,348

APPARATUS FOR AIR IMPINGEMENT STARTING OF A TURBOJET ENGINE Filed Nov. 25, 1959 PHIL /P R. PA/EMENT United States Patent 2,989,848 APPARATUS FOR AIR IMPINGEMENT STARTING OF A TURB'OJET ENGINE Phihp R. Paiement, Melrose, Mass., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed Nov. 25, 1959, Ser. No. 855,481 2 Claims. (Cl. Gil-39.14)

The present invention relates to the air impingement starting of a gas turbine engine and more particularly to the starting of a gas turbine engine by impinging on the rotary blades a discharge of air from channels located in the stator vanes of the engine.

Present impingement starters for gas turbine engines use discrete nozzles either directly over the turbine wheel or over the turbine nozzle diaphragm. The starters employing the nozzles directly over the turbine wheel impinge air directly against the thin tips of the rotary blades while the nozzles employed over the turbine nozzle diaphragm impinge air at a thicker part of the rotary blade. Both starters locate the nozzles out of the primary air passage so as not to produce any harmful excitation of the turbine wheel during normal engine operation when the starter is not in use. In so locating the nozzles the efliciency of the starter is low since the air discharged through a nozzle is at an angle to the flow of the primary air and at an angle other than 90 to a radial line through the blade resulting in undesirable and wasteful vertical force components. One method which has been used to eliminate the undesirable vertical force components is to discharge the starter air through openings in the trailing edges of the stator vanes, however, this method requires slots in the trailing portion of the vane as a passage for the air resulting in the trailing portion having a thickness of twice the normal thickness plus the width of the passage required. In such a method a heavier and more cumbersome vane is required and there is a separation of the gas flow during engine operation all contributing to inefiicient turbine performance. In the present invention the above stated difficulties are overcome by discharging the starter air from channels opening in the concave side of the vane. Each channel directs the starter air at an angle perpendicular to a radial line of the engine through the trailing edge of the vane and parallel to the flow of the primary air over the vane thus eliminating all undesirable vertical force components and keeping the trailing edge thickness at a minimum.

An object of the present invention is to provide a more efiicient starter for a turbine engine.

Another object is to provide a starter for a turbine engine which has no projections in the path of the primary air.

Still another object is to provide a starter for a turbine engine which does not cause a separation of the gas flow during engine operation.

Still another object is to provide a starter for a turbine engine of the type where starter air is ejected from the stator vanes, the vanes being of a minimum thickness at the trailing edge portion.

Still another object is to provide a starter for a turbine engine which causes no undesirable vertical force components.

Still another object is to provide a starter for a turbine engine of the type where starter air is ejected from the stator vanes at an angle parallel to the flow of primary air over the vanes.

A fiurther object of the invention is to provide a means for more efliciently cooling the turbine blades.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 shows a cross-sectional view of the stator vanes and rotor blades.

FIG. 2 shows a plan view, partly in section of a stator vane and rotor blade.

Referring now to the drawings, wherein like reference characters designate like parts throughout the several views 3 represents the stator vanes of a turbine engine each vane 3 having a cavity 4 and a channel 5 opening on the concave side of the vane. Channel 5 impinges starter air on rotor blades 7 at an angle B which is the same angle of impingement inflicted by the flow of primary air. When check valve 9 is opened starter air flows into manifold 8 and then into the cavities 4 of the individual stator vanes 3 whereupon it is ejected from channels 5 and impinged on rotor blades 7, the ejection of the starter air being along a path 11 which is perpendicular to a radial line 13 from the centerline of the engine passing through a trailing edge 12. Essentially, the channels 5 are positioned so that the starter air is impinged on the rotor blades at the same angle that the primary air is impinged on the rotor blades. It is to be noted that the channels 5 may be of any dimensions depending upon the starter requirements of the engine.

In order to start a turbine engine employing the invention described, a check valve 9 is opened allowing starter air to impinge on the rotor blades 7. When the engine becomes self-sustaining, check valve 9 is closed so that the starter air flow is terminated. If it is desired to cool the rotor blades 7 or the stator vanes 3 during the normal running operation of the engine, the starter air or any other gas may be introduced through the vanes 3 by leaving the check valve 9 in an open position during operation of the turbine by the primary air.

It is to be understood that a starter gas may be employed in lieu of the starter air mentioned throughout the disclosure depending upon the design of the engine.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A means for starting a turbojet engine comprising, a series of curved stator vanes and a series of rotor blades aligned to receive a primary flow of gas therethrough, each of said stator vanes having a cavity therein, a manifold for connecting the cavities of each of said stator vanes, a check valve for admitting compressed gas into said manifold, each stator vane having at least one channel of constant cross sectional area leading from the cavity and opening on the concave side of said stator vane, said channel being positioned so that gas is ejected therefrom and impinges on a single rotor blade at any one moment at the same angle that the primary flow of gas strikes said rotor blades.

2. A means for starting a turbojet engine comprising, a series of curved stator vanes and a series of rotor blades aligned to receive a flow of gas therethrough, each of said stator vanes having a leading and trailing edge and a cavity therein, a manifold for interconnecting the cavities of each of said stator vanes, a check valve for admitting compressed gas into said manifold, each stator vane having at least one channel leading from the cavity and opening on the concave side of said stator vane, said channel being positioned so that the gas is ejected therefrom in a path which is substantially perpendicular to said trailing edge of said stator vane and said channel positioned so that the gas strikes said rotor blades at the same angle that asid flow of gas strikes said rotor blades.

References Cited in the file of this patent UNITED STATES PATENTS 2,489,683 Stalker NOV. 29, 1949 10 2,647,368 Triebbnigg et al Aug. 4, 1953 2,714,802 Wosika Aug. 9, 1955 

